Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[gregj]

Alan, you obviously haven't driven on Australian roads...
Unsprung mass problem is highlighted by racing, but not confined to to. Simple scenario: Coming up to a corner anything over about 20kph. Dip or bump unseen on the entrance with a square(enough) edge with a transient height greater than the defection limit of the rear tyre. When the tyre hits that mass will be chucked upwards. With a low unsprung rear mass the suspension can absorb the deflection as the spring acts against a much greater motorcycle/rider mass. With large unprung rear mass the correct weight spring rate to suspend the relatively lighter motorcycle/rider mass will blow through it's travel and continue upwards. Not conducive to safety. I have had this happen on the old CX500 which had a very heavy shaft drive "diff" . Didn't crash, but I was luckily going in a straight line , not cornering.

[Crissa]

You guys keep acting like these motors are hugely heavy.  They're not.

It's not as good as a lightweight racing wheel, but it's not much worse than an old cruiser wheel.

Before whining about 'unsprung weight' maybe look into the weight of the wheel-motor assembly you're complaining about and compare it to the range otherwise possible.

If we're skimping on the motor here, why wouldn't we be otherwise looking at a cheap steel (heavy) wheel as the alternative?

This isn't the performance model, anyhow.

-Crissa

[princec]

It's all about relative weight of sprung to unsprung mass and there doesn't appear to be a lot of sprung mass and rather more sprung mass than usual, which is essentially the worst combination. That's not what worries me about the design though. Look at how the swingarm pivots on the frame. Ahh.

Cas

[caza]

For reference, Sondors says it's an 8KW nominal motor. Here's a comparable hub motor from QS, the biggest maker of hub motors for this application and very likely where Sondors is sourcing their motor.

https://www.aliexpress.com/item/1005001694402620.html

It's 23kgs, or 50lbs.

Sondors claims their entire bike weights 200lbs.

1/4 of your bikes weight in the rear wheel is significant.

In comparison, a honda grom is 233lbs, and its OEM rear wheel is only 7lbs.

I think it would be naïve to assume that the sondors having so much of its total weight in the rear wheel wouldn't effect handling.

But I also think most entry level riders who would be most interested in this would not notice or care for the difference. It's not meant for the track, it's not meant for stunt riding. People who buy the metacycle are going to be commuting at city speeds in it for the most part, and under those conditions the handling difference isn't going to be the end of the world.

Yes, if you go around a corner blazing fast on this thing on a bumpy road it might walk on you and it's not going to behave nearly as well as a bike with less unsprung weight, but a new rider shouldn't be doing that! Anyone riding this thing should simple be aware of its limitations and ride within them.

There are a lot of things about all of our bikes that are not ideal, and we all have to know the risks that come with those and act accordingly. Before the SR/F none of the zeroes had TC or  dual front discs, so there was a potential for spinning the rear wheel and our stopping distance wasn't ideal. That didn't make the zero an inherently bad bike or not worth buying. It's just a compromise that was made and we had to manage the drawbacks of.

A rear hub is no different. It's a compromise that has drawbacks, and we should be aware of them. To me this isn't a dealbreaker for the Sondors, giving all the other benefits its bringing for its price point and its ideal use, the hub motor is suites the bike just fine. Someone buying the bike should be aware of how unsprung weight effects handling and ride accordingly.

If you go to a community like elmoto.net or endless-sphere, you'll see a ton of people with heavy hub motors similar to this one that really enjoy their bikes. Sometimes the on-paper ideal is not relevant to the individual experience.

[Crissa]

But the rider weighs 200lbs.  They're part of the load.

And again, you're comparing an ultra light-weight wheel against a cheap wheel.  That is not, at all, honest.

-Crissa

[caza]

The rider weighs 200lbs on the grom, the rider weighs 200lbs on the sondors.

The sondors has 40+ more lbs unsprung rotating weight in the rear wheel than the grom.

This effects handling. That's just a fact.

How much that handling difference actually matters to the rider is definitely up for debate. Personally I think it's not a big deal in this case, but to say it has no effect at all is to ignore known motorcycle handling characteristics, and y'know, physics.

I don't know what you mean about ultra-light wheel against a cheap wheel? I chose the grom because it has a roughly similar weight to the sondors, that OEM wheel is not some special ultra-light wheel, but its the wheel honda engineers chose to be a part of that system. Cost is irrelevant.

[Fran K]

Besides the hub motor, spokes and nipples, rim, rim band, tube, tire, brake rotor and caliper, some wires.

I probably speculated about the relative weight on the tires earlier.

[caza]

Sure, those are all factors in unsprung weight, but they should be relatively similar between the grom and the sondors. The biggest difference in weight is simply adding the hub motor.

[Crissa]

Again, you're weighing a performance wheel against a cheap wheel.

Why?  They are not in the same league.

One doesn't have a chain or sprocket, either.  You're not weighing that, either.

The more you back-pedal, the smaller the difference is.

-Crissa

[caza]

Performance wheel? I honestly don't understand what you're talking about.

And backpedal? I've been pretty consistant. A hub motor is more unsprung weight, that effects handling, this is what I've said consistantly. I've also said it probably isn't a big deal to the rider, again consistantly.

Where's the backpedal? What point are you trying to make?

[Crissa]

You don't, because you're comparing a budget electric to a performance 125?

-Crissa

[JaimeC]

You don't, because you're comparing a budget electric to a performance 125?

-Crissa

When was the "Grom" a performance bike?  I't s a PLAY bike.  Racers use them in the pits.  People putter around town on them.

And fifty pounds (you DID see that part, right) is FIFTY POUNDS.  I don't care how many sprockets and chains you put on that wheel, unless you built the sprocket out of depleted uranium it isn't going to weigh anywhere near fifty pounds.

[princec]

Now you think about it I wonder what the reasoning was for putting such a huge weight in the hub like that when there's ... a giant hole in the frame. Like, it seems there's space to spare to have moved things around a bit and I don't think a chain and sprockets would have hurt to add. Hey ho. It does look fabulous though.

Cas

[TheRan]

Because they're going to fill that hole with storage, a faster charger, or more battery. One of the advantages of hub motors is it frees up space for other components. The other advantages are that it's a bit simpler and cheaper to design and build (good for hitting that $5k target), less maintenance, and it looks neat which is obviously a big part of the appeal of this bike.

[caza]

The grom, a performance bike?